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Vaudreuil-Soulanges is part of the St Lawrence Valley. Two million years ago the region was subject to a series of glaciations that covered much of North America. The last in the series was the Wisconsin glaciation. The ice sheet weighed down the landscape. This created the depressions in the land that created the basins for Lake Saint-Louis, Lac des Deux-Montagnes and Lake Saint-Francis. As the ice sheet eroded, the region was mostly submerged 12000 years ago by an inland saltwater sea known as the Champlain sea. Once the glacier was melted, the land rose again, pushing the saltwater into the sea. 10000 years ago the body of water, now a fresh water lake, has been named by scholars as Lake Lampsilis.

Canton Newton (modern day Sainte-Justine-de-Newton, not part of the seigneurie system, was modeled after British township system)[10][better source needed]

The seigneurial system was finally abolished in 1854, nearly a century after Great Britain took over the territory after defeating France in the Seven Years' War.

It is the only county in Quebec that is south of the Ottawa River. Great Britain wanted to keep most of the French-speaking, ethnic French population of the area within Lower Canada during the 1791 division of Upper and Lower Canada (precursors to the provinces of Ontario and Quebec). It is geographically isolated from the Montérégie region, as it is its only county located north of the St. Lawrence River.